What should the thickness of each layer be based upon?

The thickness of each layer in a roadway construction project should indeed be based on design specifications. Design specifications are established guidelines detailing the necessary parameters and dimensions that ensure the structural integrity and durability of the roadway. These specifications take into account various factors including traffic loads, material properties, and local environmental conditions to determine the optimal layer thickness for performance.

While environmental effects, layer composition, and weather conditions are important considerations in the construction process, they are often evaluated as part of the overall design specifications rather than directly dictating the thickness. For instance, design specifications would consider how certain materials behave under specific environmental conditions or how different compositions affect the necessary thickness for supporting the anticipated loads. By adhering to design specifications, engineers ensure that the roadway meets safety and functionality standards over its intended lifecycle.